Kateryna Gandzyuk's death in November sparked condemnation of the government and drew renewed attention to dozens of assaults on other anti-corruption campaigners in Ukraine

Ukrainian President Petro Poroshenko on Friday refused to accept the resignation of his top prosecutor over the death of an anti-corruption campaigner following a horrific acid attack, his office said.

The announcement came just hours after a top EU official urged Ukrainian authorities to identify and punish those responsible for the high-profile crime.

Kateryna Gandzyuk, who worked as an adviser to the mayor of the southern city of Kherson, was attacked in July and had about a litre of acid poured on her.

The 33-year-old died on Sunday after months of treatment including more than ten surgeries, sparking fresh condemnation of the government.

Civil society activists accuse the authorities of failing to complete the investigation or find out who ordered the attack.

General Attorney Yuriy Lutsenko this week submitted a letter of resignation to Poroshenko over the affair.

A representative of Poroshenko's office said he had rejected Lutsenko's resignation, noting that lawmakers failed to approve his dismissal in a test vote in parliament this week.

"He is facing important tasks," the representative told AFP in written comments on Friday.

The growing controversy poses a new embarrassment for the pro-Western leader who is expected to run for re-election next year.

- 'Deeply shocked' -

Just a few hours earlier EU Enlargement Commissioner Johannes Hahn said during a visit to Kiev that the international community was "deeply shocked" by the tragedy.

"It's something we cannot accept," he told a news conference, urging the Ukrainian government to identify and punish those who have ordered the attack.

"We all to have work hard to clear up this crime," he said. "The international community pays attention."

Police have detained two people and another three have been placed under house arrest but the mastermind is believed to be at large.

Two Ukrainian journalists have alleged that an aide to a lawmaker from Poroshenko's party may have acted as an intermediary in the attack.

The assistant, Igor Pavlovsky, has confirmed that he was questioned as a witness but denied being involved.

Gandzyuk was an outspoken critic of corruption in law enforcement agencies. She was hospitalised with burns on more than 30 percent of her body, including her upper torso, arms, and face.

Her death has drawn fresh attention to a spate of assaults on other anti-corruption campaigners over the past few months.

Post-Soviet Ukraine, which is locked in a conflict with pro-Russian separatists in the industrial east, dreams of joining the European Union.

Poroshenko's government has sought to overhaul the law enforcement agencies and push through other ambitious reforms, but critics say corruption is still rampant and many attacks on activists and journalists remain unpunished.